Zoom lens system

ABSTRACT

A zoom lens system which includes, in order from an object side, a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a positive refractive power, a space between the lens units is changed to perform magnification change; a lens of the second lens unit closest to an image side has a concave surface which faces the image side; a lens of the third lens unit closest to the object side is a negative lens whose concave surface faces the object side; and during the magnification change, the space between the second lens unit and the third lens unit is larger in a telephoto end than in a wide-angle end.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. §119 of Japanese patentapplication of No. 2006-102736 filed on Apr. 4, 2006, the contents ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens system.

2. Description of the Related Art

In recent years, a digital camera has received considerable attention asthe next-generation camera instead of a 35 mm film camera. Furthermore,the camera has several categories in a broad range from amulti-functional type for business use to a portable popular type. Thepresent invention especially pays attention to the portable popular typeof category, and aims to provide a technology of realizing a thin videocamera and a thin digital camera while securing high image qualities.

Thinning of the camera in a depth direction is hampered most by athickness of an optical system, especially a zoom lens system from thesurface closest to an object side to an image pickup surface. In recentyears, it has been a mainstream to use a so-called collapsible lensbarrel so that the optical system is projected from a camera body duringphotographing and stored in the camera body during carrying.

To realize the thinning and miniaturization, an image sensor may beminiaturized. However, to obtain the same number of pixels, pixelpitches need to be reduced. In this case, the image sensor has aninsufficient sensitivity. This has to be covered by the optical system.When the pixel pitches decrease, the image quality is adversely affectedby deterioration of a resolution due to diffraction. This also has to becovered by the optical system. Therefore, a bright optical system havinga small F-number is required. Furthermore, to satisfy a demand that auser desires to enjoy a broad range of photographing, a zoom lens systemhaving a large angle of field in a wide-angle end and having a largezoom ratio is demanded.

Examples of a comparatively compact zoom lens system having a zoom ratiowhich is as high as about threefold and having a large angle of fieldare disclosed in Japanese Patent Application Laid-Open Nos. 2004-318099,2004-318106 and 2004-318107.

Each of these zoom lens systems has, in order from an object side, afirst lens unit having a negative refractive power, a second lens unithaving a positive refractive power and a third lens unit having apositive refractive power. An axial space between lenses constitutingthe first lens unit is reduced, the first lens unit is constituted ofonly one negative lens, or an inner focusing system is adopted. Inconsequence, a zoom lens system having a comparatively compact lensbarrel when collapsed is realized.

SUMMARY OF THE INVENTION

A zoom lens system of the present invention comprises, in order from anobject side, a first lens unit having a negative refractive power, asecond lens unit having a positive refractive power and a third lensunit having a positive refractive power, a space between the lens unitsis changed to perform magnification change, a lens of the second lensunit closest to an image side has a concave surface which faces theimage side, a lens of the third lens unit closest to the object side isa negative lens whose concave surface faces the object side, and thespace between the second lens unit and the third lens unit becomeslarger in a telephoto end than in a wide-angle end for the magnificationchange.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given below and the accompanying drawings, whichare given by way of illustration only and thus are not limitative of thepresent invention, wherein:

FIGS. 1A to 1C are sectional views of Example 1 of a zoom lens systemaccording to the present invention when focused on an infinite object,FIG. 1A is a sectional view in a wide-angle end, FIG. 1B is a sectionalview in an intermediate state, and FIG. 1C is a sectional view in atelephoto end;

FIGS. 2A to 2C are sectional views of Example 2 of a zoom lens systemaccording to the present invention when focused on an infinite object,FIG. 2A is a sectional view in a wide-angle end, FIG. 2B is a sectionalview in an intermediate state, and FIG. 2C is a sectional view in atelephoto end;

FIGS. 3A to 3C are sectional views of Example 3 of a zoom lens systemaccording to the present invention when focused on an infinite object,FIG. 3A is a sectional view in a wide-angle end, FIG. 3B is a sectionalview in an intermediate state, and FIG. 3C is a sectional view in atelephoto end;

FIGS. 4A to 4C are sectional views of Example 4 of a zoom lens systemaccording to the present invention when focused on an infinite object,FIG. 4A is a sectional view in a wide-angle end, FIG. 4B is a sectionalview in an intermediate state, and FIG. 4C is a sectional view in atelephoto end;

FIGS. 5A to 5C are sectional views of Example 5 of a zoom lens systemaccording to the present invention when focused on an infinite object,FIG. 5A is a sectional view in a wide-angle end, FIG. 5B is a sectionalview in an intermediate state, and FIG. 5C is a sectional view in atelephoto end;

FIGS. 6A to 6C are sectional views of Example 6 of a zoom lens systemaccording to the present invention when focused on an infinite object,FIG. 6A is a sectional view in a wide-angle end, FIG. 6B is a sectionalview in an intermediate state, and FIG. 6C is a sectional view in atelephoto end;

FIGS. 7A to 7C are sectional views of Example 7 of a zoom lens systemaccording to the present invention when focused on an infinite object,FIG. 7A is a sectional view in a wide-angle end, FIG. 7B is a sectionalview in an intermediate state, and FIG. 7C is a sectional view in atelephoto end;

FIGS. 8A to 8C are diagrams showing a spherical aberration (SA), anastigmatism (FC), a distortion (DT) and a chromatic aberration ofmagnification (CC) of Example 1 when focused on the infinite object,FIG. 8A is an aberration diagram in the wide-angle end, FIG. 8B is anaberration diagram in the intermediate state, and FIG. 8C is anaberration diagram in the telephoto end;

FIGS. 9A to 9C are diagrams showing a spherical aberration (SA), anastigmatism (FC), a distortion (DT) and a chromatic aberration ofmagnification (CC) of Example 2 when focused on the infinite object,FIG. 9A is an aberration diagram in the wide-angle end, FIG. 9B is anaberration diagram in the intermediate state, and FIG. 9C is anaberration diagram in the telephoto end;

FIGS. 10A to 10C are diagrams showing a spherical aberration (SA), anastigmatism (FC), a distortion (DT) and a chromatic aberration ofmagnification (CC) of Example 3 when focused on the infinite object,FIG. 10A is an aberration diagram in the wide-angle end, FIG. 10B is anaberration diagram in the intermediate state, and FIG. 10C is anaberration diagram in the telephoto end;

FIGS. 11A to 11C are diagrams showing a spherical aberration (SA), anastigmatism (FC), a distortion (DT) and a chromatic aberration ofmagnification (CC) of Example 4 when focused on the infinite object,FIG. 11A is an aberration diagram in the wide-angle end, FIG. 11B is anaberration diagram in the intermediate state, and FIG. 11C is anaberration diagram in the telephoto end;

FIGS. 12A to 12C are diagrams showing a spherical aberration (SA), anastigmatism (FC), a distortion (DT) and a chromatic aberration ofmagnification (CC) of Example 5 when focused on the infinite object,FIG. 12A is an aberration diagram in the wide-angle end, FIG. 12B is anaberration diagram in the intermediate state, and FIG. 12C is anaberration diagram in the telephoto end;

FIGS. 13A to 13C are diagrams showing a spherical aberration (SA), anastigmatism (FC), a distortion (DT) and a chromatic aberration ofmagnification (CC) of Example 6 when focused on the infinite object,FIG. 13A is an aberration diagram in the wide-angle end, FIG. 13B is anaberration diagram in the intermediate state, and FIG. 13C is anaberration diagram in the telephoto end;

FIGS. 14A to 14C are diagrams showing a spherical aberration (SA), anastigmatism (FC), a distortion (DT) and a chromatic aberration ofmagnification (CC) of Example 7 when focused on the infinite object,FIG. 14A is an aberration diagram in the wide-angle end, FIG. 14B is anaberration diagram in the intermediate state, and FIG. 14C is anaberration diagram in the telephoto end;

FIG. 15 is a front perspective view showing an appearance of a digitalcamera using the zoom lens system of the present invention;

FIG. 16 is a rear view of the digital camera of FIG. 15;

FIG. 17 is an explanatory view showing an inner constitution of thedigital camera of FIG. 15;

FIG. 18 is a schematic block diagram showing a main part of a controlsystem of the digital camera shown in FIG. 15;

FIG. 19 is a front view of a cellular phone;

FIG. 20 is a sectional view of a photographing optical systemincorporated in the cellular phone;

FIG. 21 is a side view of the cellular phone; and

FIG. 22 is a schematic block diagram showing a main part of a controlsystem related to photographing, image recording and image display ofthe cellular phone of FIG. 19.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will hereinafter be described in detail inaccordance with examples.

As described above, a zoom lens system of the present inventioncomprises a first lens unit having a negative refractive power.According to such a negative-lead type lens constitution, even when atotal length is reduced, an appropriate zoom ratio can be secured, andan angle of field in a wide-angle end is easily secured. Furthermore,even when the angle of field becomes large in the wide-angle end, anouter diameter of a lens closest to an object side can comparatively bereduced.

Moreover, a lens of a second lens unit closest to an image side has aconcave surface facing the image side, and a lens of a third lens unitclosest to the object side is a negative lens whose concave surfacefaces the object side. In consequence, the third lens unit efficientlyand easily cancels off-axial aberrations generated in the first andsecond lens units. Specifically, the concave surface of the second lensunit closest to the image side kicks up a ray to increase a ray height.In this state, an off-axial ray is allowed to enter the negative lens ofthe third lens unit closest to the object side, whose concave surfacefaces the object side. In consequence, an astigmatism, a distortion anda chromatic aberration of magnification generated in the first lens unitcan be cancelled by the third lens unit. Since the second lens unitbears a function of magnification change, a spherical aberration, thedistortion and a coma are easily generated, but the aberrations can becancelled by the third lens unit. When this third lens unit is movedindependently of another lens unit during the magnification change, anaberration fluctuation in the whole magnification change region issuccessfully minimized.

As described later, it is advantageous to adopt an inner focusing systemfor achieving a compact lens barrel. However, since the above lensconstitution is adopted, the aberration fluctuations duringphotographing of a short-distance object can be minimized in a casewhere the third lens unit is used to perform inner-focusing. During themagnification change, the lens units are moved so that a space betweenthe second lens unit and the third lens unit is larger in a telephotoend than in the wide-angle end. In consequence, the third lens unit canhave a function of increasing magnification in a magnification changerange from the vicinity of an intermediate focal length state to thetelephoto end. Therefore, a burden on the second lens unit which is amain magnification change unit can be reduced, and the aberrationfluctuation during the magnification change can further be reduced.Since a movement amount of the second lens unit can be reduced, theconstitution also contributes to the compact lens barrel.

In addition, when the following constitutions and conditions aresatisfied, a further compact zoom lens system can be realized, and asatisfactory optical performance can be secured.

The first lens unit may be configured to move along a locus which isconvex toward the image side during the magnification change. The secondlens unit may be moved to the only object side. According to such aconstitution, a telecentricity on the image-side is improved, and a raycan efficiently be allowed to enter an image sensor (e.g., a CCD imagesensor). Since a back focus (a distance between a rearmost lens surfaceof the zoom lens system and an image surface thereof) can be lengthened,it is possible to secure a space where members such as an optical lowpass filter and an infrared cut filter are arranged. While anappropriate exit pupil distance is kept, the total length of the zoomlens system can be reduced.

The focusing on an object at a short distance may be performed by movingthe third lens unit. An inner focusing system by moving the third lensunit is advantageous for miniaturization as compared with a focus systemby moving the zoom lens system as a whole or by moving the first lensunit. For example, since the moving lens unit is light, a load on amotor is small, and the total length does not increase. Since a drivingmotor can be disposed in the lens barrel, a size of the lens barrel in adiametric direction does not increase.

The third lens unit may be constituted of two lenses including anegative lens and a positive lens in order from an object side. Anoff-axial ray emitted from the second lens unit and passed through thethird lens unit easily forms a large angle with respect to an opticalaxis. However, according to such a constitution, the angle of theoff-axial ray passed through the third lens unit can be reduced withrespect to the optical axis. Therefore, even when the third lens unit ismoved, the fluctuations of the off-axial aberrations, especially anastigmatism and a coma can be reduced. Since an axial marginal ray has asmall angle with respect to the optical axis, the fluctuations of thespherical aberration during the focusing are reduced. Therefore, it ispossible to secure a satisfactory performance during the focusing on theobject at the short distance by the third lens unit.

At this time, it is preferable that the negative lens and the positivelens of the third lens unit satisfy the following condition:−4.2<f _(3n) /f _(3p)<−1.1  (1),in which f_(3n) is a focal length of the negative lens of the third lensunit, and f_(3p) is a focal length of the positive lens of the thirdlens unit.

If a value of f_(3n)/f_(3p) exceeds an upper limit of −1.1 in thecondition (1), an excessive amount of a negative distortion in thewide-angle end is generated. If the value lowers below a lower limit of−4.2, a function of reducing the angle of the off-axial ray passedthrough the third lens unit diminishes. Therefore, the fluctuations ofthe astigmatisme and the coma during the focusing of the third lens unitincrease, and it is difficult to secure an optical performance duringthe photographing of the object at the short distance.

It is more preferable to satisfy the following condition:−3.50<f _(3n) /f _(3p)<−1.50  (1)′.

In addition, it is further preferable to satisfy the followingcondition:−2.80<f _(3n) /f _(3p)<−1.90  (1)″.

The negative lens of the third lens unit closest to the object side maysatisfy the following condition:−7.90<SF _(3n)<−1.20  (2).Here SF_(3n) is defined by “SF_(3n)=(R_(31f)+R_(31r))/(R_(31f)−R_(31r))”and in which R_(31f), R_(31r), are paraxial radii of curvatures of anobject-side surface and an image-side surface of the negative lens ofthe third lens unit, respectively.

If a value of SF_(3n) exceeds an upper limit of −1.20 in the condition(2), the function of reducing the angle of the off-axial ray passedthrough the third lens unit diminishes. Therefore, the fluctuations ofthe astigmatism and the coma during the focusing of the third lens unitincrease, and the optical performance during the photographing of theobject at the short distance cannot be secured. If the value lowersbelow a lower limit of −7.90, the Petzval sum deteriorates. The fieldcurvature is overcorrected, and the image surface largely curves towarda plus side. An excessively large positive distortion is generated inthe telephoto end. Furthermore, since a lens peripheral portionprotrudes toward the object side, the negative lens interferes withanother lens disposed on the front side thereof or a mechanical memberof the lens barrel in a collapsed state, and it is difficult to reducethe thickness of the lens barrel.

It is more preferable to satisfy the following condition:−6.90<SF _(3n)<−2.20  (2)′.

In addition, it is further preferable to satisfy the followingcondition:−5.90<SF _(3n)<−3.20  (2)″.

Moreover, the negative lens of the third lens unit closest to the objectside may satisfy the following conditions:1.75<n_(d3n)<2.20  (3); and13.0<v_(d3n)<33.0  (4),in which n_(d3n) and v_(d3n) are a refractive index and the Abbe numberof the negative lens of the third lens unit closest to the object sidefor the d-line, respectively.

The condition (3) is a condition concerning a refractive index of thelens in order to appropriately inhibit the generation of the aberration.When the refractive index is increased to a certain degree, thecurvature of the lens surface can be reduced, and the generation of theaberration can be minimized. If a value of n_(d3n) exceeds an upperlimit of 2.20 in the condition (3), a vitreous material cannot easily beobtained, mass productivity deteriorates, and costs tend to increase. Ifthe value lowers below a lower limit of 1.75, the curvature of the lenssurface has to be increased in order to obtain a desired refractivepower. Therefore, excessively large spherical aberration and coma aregenerated, and it is difficult to obtain a satisfactory performance inthe whole magnification change region.

The condition (4) is a condition concerning the Abbe number of the lens,for appropriately correcting an axial chromatic aberration. If a spacebetween the lenses constituting the first lens unit is reduced or thefirst lens unit is constituted of only one negative lens in order toachieve a compact constitution, the chromatic aberration of the firstlens unit tends to be undercorrected. To solve the problem, the Abbenumber of the negative lens of the third lens unit can be set to be toappropriately correct the chromatic aberration generated in the firstlens unit. If a value of v_(d3n) exceeds an upper limit of 33.0 in thecondition (4), a dispersion of the vitreous material is excessivelysmall, and the axial chromatic aberration and the chromatic aberrationof magnification are incompletely corrected. If the value lowers below alower limit of 13.0, the vitreous material has an excessive anomalousdispersion property, and it is difficult to correct a secondary spectrumof the axial chromatic aberration and the chromatic aberration ofmagnification. Therefore, a color blur is easily generated in aphotographed image. Alternatively, the number of the lenses constitutingthe zoom lens system has to be increased in order to correct thesecondary spectrum of the chromatic aberration, the costs increase, andthe zoom lens system cannot be constituted to be compact.

Regarding the condition (3), it is more preferable to satisfy thefollowing condition:1.83<n_(d3n)<2.05  (3)′.

Furthermore, it is further preferable to satisfy the followingcondition:1.90<n_(d3n)<1.95  (3)″.

Regarding the condition (4), it is more preferable to satisfy thefollowing condition:15.0<v_(d3n)<29.0  (4)′.

Furthermore, it is further preferable to satisfy the followingcondition:17.0<v_(d3n)<22.0  (4)″.

In addition, the space between the second lens unit and the third lensunit may satisfy the following condition:0.35<d ₂₃ /f _(w)<1.25  (5),in which d₂₃ is an axial space between the second lens unit and thethird lens unit in the wide-angle end, and f_(w) is a focal length ofthe zoom lens system in the wide-angle end.

If a value of d₂₃/f_(w) exceeds an upper limit of 1.25 in the condition(5), the field curvature and the distortion in the wide-angle end areinsufficiently corrected. If the value lowers below a lower limit of0.35, a space for moving the lens units during the focusing of the thirdlens unit falls short, and the shortest object distance that can befocused is limited.

It is more preferable to satisfy the following condition:0.45<d ₂₃ /f _(w)<1.00  (5)′.

Furthermore, it is further preferable to satisfy the followingcondition:0.55<d ₂₃ /f _(w)<0.75  (5)″.

To realize a compact optical system, it is preferable that the firstlens unit is constituted of two or less lenses.

To achieve a further compact constitution, the first lens unit may beconstituted of only one negative lens.

At this time, since the aberrations generated in the first lens unitcannot be cancelled in the unit, the aberration generation needs to beinhibited to such a realistic extent that the photographed image can beappreciated. Therefore, it is preferable to develop the followingvarious devises.

It is preferable that the negative lens of the first lens unit satisfiesthe following condition:75.0<v_(d1n)<105.0  (6),in which v_(d1n), is the Abbe number of the negative lens of the firstlens unit.

If a value of v_(d1n) exceeds an upper limit of 105.0 in the condition(6), it is difficult to obtain the vitreous material, the massproductivity deteriorates, and the costs easily increase. If the valuelowers below a lower limit of 75.0, an excessively large chromaticaberration is generated, and the color blur of the photographed image iseasily generated.

It is more preferable to satisfy the following:80.0<v_(d1n)<100.0  (6)′.

In addition, it is further preferable to satisfy the following:90.0<v_(d1n)<96.0  (6)″.

Moreover, it is preferable that the negative lens of the first lens unitsatisfies the following condition:0.01<SF_(1n)<1.00  (7).Here SF_(1n) is defined by “SF_(1n)=(R_(11f)+R_(11r))/(R_(11f)−R_(11r))”and in which R_(11f), R_(11r) are paraxial radii of curvatures of anobject-side surface and an image-side surface of the negative lens ofthe first lens unit, respectively.

The condition (7) is a condition for achieving a good balance betweenthe miniaturization and the aberrations. If a value of SF_(1n) exceedsan upper limit of 1.00 in the condition (7), an excessively largespherical aberration is generated in the first lens unit. Therefore, thefluctuations of the spherical aberration during the magnification changeincrease, and it is difficult to secure a satisfactory opticalperformance in the whole magnification change region. If the valuelowers below a lower limit of 0.01, an absolute value of the curvatureof a concave surface on an incidence side increases, and the distortionand the astigmatism in the wide-angle end are not easily suppressed.

It is more preferable to satisfy the following condition:0.07<SF_(1n)<0.70  (7)′.

In addition, it is further preferable to satisfy the followingcondition:0.13<SF_(1n)<0.40  (7)″.

Moreover, it is preferable that the negative lens of the first lens unithas aspherical surfaces on the object-side surface and the image-sidesurface. According to such a constitution, the field curvature and thedistortion can effectively be corrected. At this time, the asphericalsurface of the first lens unit may be an aspherical surface formed sothat the negative refractive power of a portion on the surface weakensas the portion comes away from the optical axis. At the first lens unit,the off-axial ray having a large incidence height easily has a largeincidence angle. Therefore, according to the above constitution, theincidence angle of the off-axial ray having the large incidence heightis inhibited from being excessively enlarged, and the generation of theaberrations can easily be inhibited.

The second lens unit is a unit which mainly performs the magnificationchange. Therefore, to obtain a satisfactory optical performance, thegeneration of the aberration needs to be minimized. Therefore, it ispreferable to develop the following devises.

As described above, it is preferable that the surface of the second lensunit closest to the image side is a concave surface facing the imageside. At this time, it is preferable to satisfy the following condition:0.44<R _(2r) /f _(w)<1.00  (8),in which R_(2r) is a par axial radius of curvature of the surface of thesecond lens unit closest to the image side, and f_(w) is a focal lengthof the zoom lens system in the wide-angle end.

If a value R_(2r)/f_(w) exceeds an upper limit of 1.00 in the condition(8), the refractive power of this surface excessively weakens, and aneffect of kicking up the ray is reduced. Then, the ray entering thethird lens unit does not have a sufficient height. Therefore, off-axialaberrations such as the astigmatism, the distortion and the chromaticaberration of magnification generated in the first lens unit cannot becancelled. If the value lowers below a lower limit of 0.44, therefractive power of this surface excessively strengthens. Therefore,excessively large spherical aberration and coma are generated in thesecond lens unit, and it is difficult to obtain a satisfactory opticalperformance in the whole magnification change region.

It is more preferable to satisfy the following condition:0.50<R _(2r) /f _(w)<0.80  (8)′.

In addition, it is further preferable to satisfy the followingcondition:0.56<R _(2r) /f _(w)<0.68  (8)″.

The second lens unit may be constituted of, in order from the objectside, a positive lens and a cemented lens of a positive lens and anegative lens. According to such a constitution, a front principal pointof the second lens unit can be shifted toward the object side.Therefore, the movement amount of the second lens unit during themagnification change can be reduced. Since the cemented lens isdisposed, the axial chromatic aberration generated in the second lensunit can be corrected.

Moreover, when the positive lens closest to the object side has twoaspherical surfaces, the coma and spherical aberration generated in thesecond lens unit can efficiently be corrected. Furthermore, when theaspherical surface is disposed on the concave surface of the second lensunit closest to the image side, the coma and the spherical aberrationcan more effectively be corrected.

Furthermore, it is preferable that the vitreous material of the lens ofthe second lens unit closest to the image side satisfies the followingconditions:1.75<n_(d2r)<2.20  (9); and15.0<v_(d2r)<50.0  (10),in which n_(d2r) and v_(d2r) are a refractive index and the Abbe numberof the lens of the second lens unit closest to the image side for thed-line.

If a value of n_(d2r) exceeds an upper limit of 2.20 in the condition(9), it is difficult to obtain the vitreous material, the massproductivity deteriorates, and the costs easily increase. If the valuelowers below a lower limit of 1.75, the curvature of the lens surfaceneeds to be enlarged in order to obtain a desired refractive power, thespherical aberration and the coma are largely generated, and thesatisfactory performance cannot be obtained in the whole magnificationchange region.

If a value of v_(d2r) exceeds an upper limit of 50.0 in the condition(10), the chromatic aberration of the second lens unit isundercorrected. If the value lowers below a lower limit of 15.0, thevitreous material tends to have an excessive anomalous dispersionproperty, and it is difficult to correct the secondary spectra of theaxial chromatic aberration and chromatic aberration of magnification.Therefore, the color blur is easily generated in the photographed image.

Regarding the condition (9), it is more preferable to satisfy thefollowing condition:1.82<n_(d2r)<2.10  (9)′.

Furthermore, it is more preferable to satisfy the following condition.1.98<n_(d2r)<2.05  (9)″.

Regarding the condition (10), it is more preferable to satisfy thefollowing condition:19.0<v_(d2r)<43.0  (10)′.

Furthermore, it is more preferable to satisfy the following condition:23.0<v_(d2r)<26.0  (10)″.

In addition, it is preferable that a focal length f₁ of the first lensunit satisfies the following condition:−4.80<f ₁ /f _(w)<−1.20  (11).

If a value of f₁/f_(w) lowers below a lower limit of −4.80 in thecondition (11), the power of the first lens unit excessively weakens,and the total length of the zoom lens system easily increases. If thevalue exceeds an upper limit of −1.20, the power of the first lens unitexcessively strengthens, and it is difficult to correct the aberration.

Furthermore, it is more preferable to satisfy the following condition:−4.00<f ₁ /f _(w)<−1.80  (11)′.

In addition, it is further preferable to satisfy the followingcondition:−3.20<f ₁ /f _(w)<−2.40  (11)″.

It is preferable that a focal length f₂ of the second lens unitsatisfies the following condition:1.00<f ₂ /f _(w)<2.00  (12).

If a value of f₂/f_(w) exceeds an upper limit of 2.00 in the condition(12), the power of the second lens unit excessively weakens, and themovement amount of the second lens unit during the magnification changeeasily increases. If the value lowers below a lower limit of 1.00, thepower of the second lens unit excessively strengthens, and it isdifficult to correct the aberration.

It is more preferable to satisfy the following condition:1.30<f ₂ /f _(w)<1.95  (12)′.

In addition, it is further preferable to satisfy the followingcondition:1.62<f ₂ /f _(w)<1.80  (12)″.

It is preferable that a focal length f₃ of the third lens unit satisfiesthe following condition:1.50<f ₃ /f _(w)<4.20  (13).

If a value of f₃/f_(w) exceeds an upper limit of 4.20 in the condition(13), the power of the third lens unit excessively weakens, and thetotal length of the zoom lens system easily increases. When the focusingat the short distance is performed by the third lens unit, the movementamount increases. Therefore, it is difficult to realize a compact lensbarrel. Further since a space for moving the third lens unit fallsshort, the photographing of a close object cannot sufficiently beperformed. If the value lowers below a lower limit of 1.50, the power ofthe third lens unit excessively strengthens, the fluctuation of theastigmatism during the focusing easily increases, and a performanceduring the photographing of the object at the short distancedeteriorates.

It is more preferable to satisfy the following condition:1.70<f ₃ /f _(w)<3.50  (13)′.

In addition, it is further preferable to satisfy the followingcondition:1.85<f ₃ /f _(w)<2.80  (13)″.

Moreover, it is preferable that the zoom lens system satisfies thefollowing condition:3.10<L _(w) /f _(w)<7.60  (14),in which L_(w) is the total length of the zoom lens system in thewide-angle end, and f_(w) is a focal length of the zoom lens system inthe wide-angle end.

If a value of L_(w)/f_(w) exceeds an upper limit of 7.60 in thecondition (14), the total length excessively increases, and it isdifficult to realize a compact lens barrel. If the value lowers below alower limit of 3.10, the powers of the lens units constituting the lenssystem excessively strengthen, an amount of the aberration to begenerated easily increases, and it is difficult to obtain a satisfactoryoptical performance.

It is more preferable to satisfy the following condition:4.10<L _(w) /f _(w)<6.80  (14)′.

In addition, it is further preferable to satisfy the followingcondition:5.10<L _(w) /f _(w)<6.10  (14)″.

Moreover, it is preferable that the zoom lens system satisfies thefollowing condition:0.60<L _(t) /f _(t)<3.00  (15),in which L_(t) is the total length of the zoom lens system in thetelephoto end, and f_(t) is a focal length of the zoom lens system inthe telephoto end.

If a value of L_(t)/f_(t) exceeds an upper limit of 3.00 in thecondition (15), the total length excessively increases, and it isdifficult to realize a compact lens barrel. If the value lowers below alower limit of 0.60, the powers of the lens units constituting the lenssystem excessively strengthen, the amount of the aberration to begenerated easily increases, and it is difficult to obtain thesatisfactory optical performance.

It is more preferable to satisfy the following condition:1.00<L _(t) /f _(t)<2.50  (15)′.

In addition, it is further preferable to satisfy the followingcondition:1.40<L _(t) /f _(t)<2.05  (15)″.

An aperture stop may be disposed between the second lens unit and thethird lens unit. According to such an arrangement, symmetry of theoptical system before and after the aperture stop is improved.Therefore, aberrations such as the coma, the field curvature, thedistortion and the chromatic aberration of magnification can furthereffectively be corrected.

Moreover, the aperture stop may be moved integrally with the second lensunit during the magnification change. In this case, since an entrancepupil can be constituted to be shallow, the constitution contributes toreduction of a diameter of the lens closest to the object side. Sincethe exit pupil can be disposed away from the image surface, theincidence angle upon the image surface can be reduced to allow the rayto efficiently enter the image sensor.

A positive or negative fourth lens unit may be disposed on the imageside of the third lens unit. The field curvature or the distortion canfurther satisfactorily be corrected. The fourth lens unit may be movedindependently of the other lens units during the magnification change.At this time, the lens units may be moved so that a space between thethird lens unit and the fourth lens unit is larger in the telephoto endthan in the wide-angle end. The chromatic aberration of magnification,the field curvature and the distortion can more effectively becorrected.

Moreover, it is preferable that the above zoom lens system satisfies thefollowing condition:5.0<Fno _(w) ×L _(w) /f _(w)<17.0  (16),in which Fno_(w) is a full aperture F-value in the wide-angle end, L_(w)is the total length of the zoom lens system in the wide-angle end, andf_(w) is a focal length of the zoom lens system in the wide-angle end.

If a value of Fno_(w)×L_(w)/f_(w) exceeds an upper limit of 17.0 in thecondition (16), the F-value or the total length unfavorably increases.If the value lowers below a lower limit of 5.0, the F-value or the totallength excessively decreases. Therefore, the power of each lens unitstrengthens, and an excessively large aberration is generated. In anycase, it is difficult to secure a sufficient optical performance.

It is more preferable to satisfy the following condition:7.0<Fno _(w) ×L _(w) /f _(w)<14.0  (16)′.

In addition, it is further preferable to satisfy the followingcondition:9.0<Fno _(w) ×L _(w) /f _(w)<11.0  (16)″.

Among the above constitutions, a plurality of constitutions mayarbitrarily be satisfied at the same time. In consequence, a moresatisfactory effect can be obtained.

Moreover, if the conditions are arbitrarily combined and satisfied, amore satisfactory effect can be obtained.

It is to be noted that in Example 1 of the present invention describedlater, the first lens unit is constituted of a cemented lens including anegative lens and a positive lens in order from the object side. Whenthe cemented lens is used, an axial air space between the lenses isremoved, and a lens barrel is constituted to be compact when collapsed.

Next, Examples 1 to 7 of a zoom lens system of the present inventionwill be described. FIGS. 1A to 7C are sectional views of Examples 1 to 7when focused on an infinite object. In the drawings, FIGS. 1A, 2A, . . .are sectional views in a wide-angle end, FIGS. 1B, 2B, . . . aresectional views in an intermediate state, and FIGS. 1C, 2C, . . . aresectional views in a telephoto end. In the drawings, a first lens unitis denoted with G1, a second lens unit is denoted with G2, an aperturestop is denoted with S, a third lens unit is denoted with G3, a fourthlens unit is denoted with G4, and an image surface is denoted with I.The reference symbol F denotes a parallel flat plate that includes a lowpass filter or the like coated with an IR cut coating and the referencesymbol C denotes a parallel flat plate which is a cover glass of anelectronic image sensor (a CCD image sensor, a CMOS type image sensor orthe like). A light receiving surface of the electronic image sensor isdisposed at a position of the image surface I. It is to be noted thatthe surface of the cover glass C may be coated with a multilayered thinfilm for limiting a wavelength band. The cover glass C may have a lowpass filter function. As shown in FIGS. 1A to 1C, a zoom lens system ofExample 1 includes, in order from an object side, a first lens unit G1having a negative refractive power, a second lens unit G2 having apositive refractive power, an aperture stop S, a third lens unit G3having a positive refractive power and a fourth lens unit G4 having apositive refractive power. During magnification change from a wide-angleend to a telephoto end, the first lens unit G1 moves while drawing alocus being convex toward an image side, and is positioned slightlycloser to the object side in the telephoto end than in the wide-angleend. The second lens unit G2 moves toward the object side integrallywith the aperture stop S. The third lens unit G3 moves toward the objectside while enlarging a space between the second lens unit G2 and thethird lens unit. The fourth lens unit G4 moves toward the image sidewhile enlarging a space between the third lens unit G3 and the fourthlens unit.

The first lens unit G1 is constituted of, in order from the object side,a double concave negative lens and a positive meniscus lens whose convexsurface faces the object side. These lenses are cemented to form acemented lens. The second lens unit G2 is constituted of, in order fromthe object side, a double convex positive lens, and a cemented lens of apositive meniscus lens whose convex surface faces the object side and anegative meniscus lens whose convex surface faces the object side. Thethird lens unit G3 is constituted of, in order from the object side, anegative meniscus lens whose convex surface faces the image side and adouble convex positive lens. The fourth lens unit G4 is constituted ofone positive meniscus lens whose convex surface faces the image side.The aperture stop S is positioned on the image side of the second lensunit G2.

Aspherical surfaces are used on nine surfaces including surfaces of thecemented lens of the first lens unit G1 closest to the object side andthe image side, opposite surfaces of the double convex positive lens ofthe second lens unit G2, a surface of the cemented lens of the secondlens unit G2 closest to the object side, opposite surfaces of the doubleconvex positive lens of the third lens unit G3, and opposite surfaces ofthe positive meniscus lens of the fourth lens unit G4.

As shown in FIGS. 2A to 2C, a zoom lens system of Example 2 includes, inorder from an object side, a first lens unit G1 having a negativerefractive power, a second lens unit G2 having a positive refractivepower, a third lens unit G3 having a positive refractive power and afourth lens unit G4 having a positive refractive power. Duringmagnification change from a wide-angle end to a telephoto end, the firstlens unit G1 moves while drawing a locus being convex toward an imageside, is positioned closer to the image side in the telephoto end thanin the wide-angle end, and is positioned slightly closer to the objectside in the telephoto end than in the intermediate state. The secondlens unit G2 moves toward the object side integrally with an aperturestop S included in the second lens unit. The third lens unit G3 movestoward the object side while enlarging a space between the second lensunit G2 and the third lens unit. The fourth lens unit G4 moves towardthe image side while enlarging a space between the third lens unit G3and the fourth lens unit.

The first lens unit G1 is constituted of one double concave negativelens. The second lens unit G2 is constituted of, in order from theobject side, a double convex positive lens, the aperture stop S and acemented lens of a positive meniscus lens whose convex surface faces theobject side and a negative meniscus lens whose convex surface faces theobject side. The third lens unit G3 is constituted of, in order from theobject side, a negative meniscus lens whose convex surface faces theimage side and a double convex positive lens. The fourth lens unit G4 isconstituted of one positive meniscus lens whose convex surface faces theobject side. The aperture stop S is positioned between the double convexpositive lens and the cemented lens of the second lens unit G2.

Aspherical surfaces are used on nine surfaces including oppositesurfaces of the double concave negative lens of the first lens unit G1,opposite surfaces of the double convex positive lens of the second lensunit G2, a surface of the cemented lens of the second lens unit G2closest to the image side, opposite surfaces of the double convexpositive lens of the third lens unit G3, and opposite surfaces of thepositive meniscus lens of the fourth lens unit G4.

As shown in FIGS. 3A to 3C, a zoom lens system of Example 3 includes, inorder from an object side, a first lens unit G1 having a negativerefractive power, a second lens unit G2 having a positive refractivepower, a third lens unit G3 having a positive refractive power and afourth lens unit G4 having a positive refractive power. Duringmagnification change from a wide-angle end to a telephoto end, the firstlens unit G1 moves while drawing a locus being convex toward an imageside, and is positioned slightly closer to the image side in thetelephoto end than in the wide-angle end. The second lens unit G2 movestoward the object side integrally with the aperture stop S. The thirdlens unit G3 moves while drawing a locus being convex toward the objectside, and is positioned closer to the object side in the telephoto endthan in the wide-angle end. The fourth lens unit G4 moves toward theimage side while once enlarging a space between the third lens unit G3and the fourth lens unit and then reducing the space.

The first lens unit G1 is constituted of one double concave negativelens. The second lens unit G2 is constituted of, in order from theobject side, a double convex positive lens, and a cemented lens of apositive meniscus lens whose convex surface faces the object side and anegative meniscus lens whose convex surface faces the object side. Thethird lens unit G3 is constituted of, in order from the object side, anegative meniscus lens whose convex surface faces the image side and adouble convex positive lens. The fourth lens unit G4 is constituted ofone positive meniscus lens whose convex surface faces the image side.The aperture stop S is positioned on the image side of the second lensunit G2.

Aspherical surfaces are used on nine surfaces including oppositesurfaces of the double concave negative lens of the first lens unit G1,opposite surfaces of the double convex positive lens of the second lensunit G2, a surface of the cemented lens of the second lens unit G2closest to the image side, opposite surfaces of the double convexpositive lens of the third lens unit G3, and opposite surfaces of thepositive meniscus lens of the fourth lens unit G4.

As shown in FIGS. 4A to 4C, a zoom lens system of Example 4 includes, inorder from an object side, a first lens unit G1 having a negativerefractive power, a second lens unit G2 having a positive refractivepower, a third lens unit G3 having a positive refractive power and afourth lens unit G4 having a positive refractive power. Duringmagnification change from a wide-angle end to a telephoto end, the firstlens unit G1 moves while drawing a locus being convex toward an imageside, and is positioned slightly closer to the image side in thetelephoto end than in the wide-angle end. The second lens unit G2 movestoward the object side integrally with an aperture stop S. The thirdlens unit G3 moves while drawing a locus being convex toward the objectside, and is positioned closer to the object side in the telephoto endthan in the wide-angle end. The fourth lens unit G4 moves toward theimage side while once enlarging a space between the third lens unit G3and the fourth lens unit and then reducing the space.

The first lens unit G1 is constituted of one double concave negativelens. The second lens unit G2 is constituted of, in order from theobject side, a double convex positive lens, and a cemented lens of apositive meniscus lens whose convex surface faces the object side and anegative meniscus lens whose convex surface faces the object side. Thethird lens unit G3 is constituted of, in order from the object side, anegative meniscus lens whose convex surface faces the image side and adouble convex positive lens. The fourth lens unit G4 is constituted ofone positive meniscus lens whose convex surface faces the image side.The aperture stop S is positioned on the image side of the second lensunit G2.

Aspherical surfaces are used on nine surfaces including oppositesurfaces of the double concave negative lens of the first lens unit G1,opposite surfaces of the double convex positive lens of the second lensunit G2, a surface of the cemented lens of the second lens unit G2closest to the object side, opposite surfaces of the double convexpositive lens of the third lens unit G3, and opposite surfaces of thepositive meniscus lens of the fourth lens unit G4.

As shown in FIGS. 5A to 5C, a zoom lens system of Example 5 includes, inorder from an object side, a first lens unit G1 having a negativerefractive power, a second lens unit G2 having a positive refractivepower, a third lens unit G3 having a positive refractive power and afourth lens unit G4 having a positive refractive power. Duringmagnification change from a wide-angle end to a telephoto end, the firstlens unit G1 moves while drawing a locus being convex toward an imageside, and is positioned slightly closer to the image side in thetelephoto end than in the wide-angle end. The second lens unit G2 movestoward the object side integrally with the aperture stop S. The thirdlens unit G3 moves while drawing a locus being convex toward the objectside, and is positioned closer to the object side in the telephoto endthan in the wide-angle. The fourth lens unit G4 moves toward the imageside while once enlarging a space between the third lens unit G3 and thefourth lens unit and then reducing the space.

The first lens unit G1 is constituted of one double concave negativelens. The second lens unit G2 is constituted of, in order from theobject side, a double convex positive lens, and a cemented lens of apositive meniscus lens whose convex surface faces the object side and anegative meniscus lens whose convex surface faces the object side. Thethird lens unit G3 is constituted of, in order from the object side, anegative meniscus lens whose convex surface faces the image side and adouble convex positive lens. The fourth lens unit G4 is constituted ofone positive meniscus lens whose convex surface faces the image side.The aperture stop S is positioned on the image side of the second lensunit G2.

Aspherical surfaces are used on nine surfaces including oppositesurfaces of the double concave negative lens of the first lens unit G1,opposite surfaces of the double convex positive lens of the second lensunit G2, a surface of the cemented lens of the second lens unit G2closest to the object side, opposite surfaces of the double convexpositive lens of the third lens unit G3, and opposite surfaces of thepositive meniscus lens of the fourth lens unit G4.

As shown in FIGS. 6A to 6C, a zoom lens system of Example 6 includes, inorder from an object side, a first lens unit G1 having a negativerefractive power, a second lens unit G2 having a positive refractivepower, a third lens unit G3 having a positive refractive power and afourth lens unit G4 having a positive refractive power. Duringmagnification change from a wide-angle end to a telephoto end, the firstlens unit G1 moves while drawing a locus being convex toward an imageside, and is positioned slightly closer to the image side in thetelephoto end than in the wide-angle end. The second lens unit G2 movestoward the object side integrally with an aperture stop S. The thirdlens unit G3 moves while drawing a locus being convex toward the objectside, and is positioned closer to the object side in the telephoto endthan in the wide-angle end. The fourth lens unit G4 moves toward theimage side while once enlarging a space between the third lens unit G3and the fourth lens unit and then reducing the space.

The first lens unit G1 is constituted of one double concave negativelens. The second lens unit G2 is constituted of, in order from theobject side, a double convex positive lens, and a cemented lens of apositive meniscus lens whose convex surface faces the object side and anegative meniscus lens whose convex surface faces the object side. Thethird lens unit G3 is constituted of, in order from the object side, anegative meniscus lens whose convex surface faces the image side and adouble convex positive lens. The fourth lens unit G4 is constituted ofone positive meniscus lens whose convex surface faces the image side.The aperture stop S is positioned on the image side of the second lensunit G2.

Aspherical surfaces are used on nine surfaces including oppositesurfaces of the double concave negative lens of the first lens unit G1,opposite surfaces of the double convex positive lens of the second lensunit G2, a surface of the cemented lens of the second lens unit G2closest to the object side, opposite surfaces of the double convexpositive lens of the third lens unit G3, and opposite surfaces of thepositive meniscus lens of the fourth lens unit G4.

As shown in FIGS. 7A to 7C, a zoom lens system of Example 7 includes, inorder from an object side, a first lens unit G1 having a negativerefractive power, a second lens unit G2 having a positive refractivepower, a third lens unit G3 having a positive refractive power and afourth lens unit G4 having a positive refractive power. Duringmagnification change from a wide-angle end to a telephoto end, the firstlens unit G1 moves while drawing a locus being convex toward an imageside, and is positioned slightly closer to the image side in thetelephoto end than in the wide-angle end. The second lens unit G2 movestoward the object side integrally with an aperture stop S. The thirdlens unit G3 moves while drawing a locus being convex toward the objectside, and is positioned slightly closer to the object side in thetelephoto end than in the wide-angle end. The fourth lens unit G4 movestoward the image side while once enlarging a space between the thirdlens unit G3 and the fourth lens unit and then reducing the space.

The first lens unit G1 is constituted of one double concave negativelens. The second lens unit G2 is constituted of, in order from theobject side, a double convex positive lens, and a cemented lens of apositive meniscus lens whose convex surface faces the object side and anegative meniscus lens whose convex surface faces the object side. Thethird lens unit G3 is constituted of, in order from the object side, anegative meniscus lens whose convex surface faces the image side and adouble convex positive lens. The fourth lens unit G4 is constituted ofone positive meniscus lens whose convex surface faces the image side.The aperture stop S is positioned on the image side of the second lensunit G2.

Aspherical surfaces are used on nine surfaces including oppositesurfaces of the double concave negative lens of the first lens unit G1,opposite surfaces of the double convex positive lens of the second lensunit G2, a surface of the cemented lens of the second lens unit G2closest to the object side, opposite surfaces of the double convexpositive lens of the third lens unit G3, and opposite surfaces of thepositive meniscus lens of the fourth lens unit G4.

Numerical data of the above examples will hereinafter be described. Inaddition to the above symbols, f is a focal length of the zoom lenssystem; F_(NO) is the F-number; 2ω is an angle of field; WE is awide-angle end; ST is an intermediate state; TE is a telephoto end; r₁,r₂ . . . are radii of curvatures of lens surfaces; d₁, d₂ . . . arespaces between the lens surfaces; n_(d1), n_(d2) . . . are refractiveindices of the lenses for the d-line; and v_(d1), v_(d2) . . . are theAbbe numbers of the lenses. A symbol * attached to data of the radius ofcurvature indicates that the surface is an aspherical surface, symbol(S) indicates that the surface is an aperture stop, and symbol (I)indicates an image surface.

It is to be noted that a shape of the aspherical surface is representedby the following equation in a coordinate system in which anintersection between the optical axis and the aspherical surface is anorigin, a z-axis is an optical axis in which a light travel direction isset to be positive, and a y-axis is an axis of an arbitrary directioncrossing the optical axis at right angle and passing the origin:z=(y ² /r)/[1+{1−(K+1)(y/r)²}^(1/2) ]+A ₄ ·y ⁴ +A ₆ ·y ⁶ +A ₈ ·y ⁸ +A ₁₀·y ¹⁰,in which r is a paraxial radius of curvature, K is a conic constant, andA₄, A₆, A₈ and A₁₀ are 4-th, 6-th, 8-th and 10-th order asphericalcoefficients.

EXAMPLE 1

r₁ = −18.164* d₁ = 0.90 n_(d1) = 1.51633 v_(d1) = 64.14 r₂ = 13.285 d₂ =1.80 n_(d2) = 1.83918 v_(d2) = 23.85 r₃ = 17.066* d₃ = variable r₄ =13.962* d₄ = 2.20 n_(d3) = 1.74320 v_(d3) = 49.34 r₅ = −25.345* d₅ =0.10 r₆ = 6.022* d₆ = 2.89 n_(d4) = 1.80610 v_(d4) = 40.92 r₇ = 119.085d₇ = 0.50 n_(d5) = 2.00069 v_(d5) = 25.46 r₈ = 4.353 d₈ = 1.72 r₉ = ∞(S) d₉ = variable r₁₀ = −8.900 d₁₀ = 0.80 n_(d6) = 1.92286 v_(d6) =18.90 r₁₁ = −12.685 d₁₁ = 0.18 r₁₂ = 64.569* d₁₂ = 2.55 n_(d7) = 1.80610v_(d7) = 40.92 r₁₃ = −13.461* d₁₃ = variable r₁₄ = −11.384* d₁₄ = 1.00n_(d8) = 1.52542 v_(d8) = 55.78 r₁₅ = −6.418* d₁₅ = variable r₁₆ = ∞ d₁₆= 0.74 n_(d9) = 1.54771 v_(d9) = 62.84 r₁₇ = ∞ d₁₇ = 0.50 r₁₈ = ∞ d₁₈ =0.50 n_(d10) = 1.51633 v_(d10) = 64.14 r₁₉ = ∞ d₁₉ = 0.55 r₂₀ = ∞ (I)

TABLE 1-1 Aspherical coefficient 1st surface 3rd surface 4th surface 5thsurface 6th surface K −0.690 −2.051 −0.478 −8.737 0.224 A₄   1.00171 ×10⁻⁴   8.63337 × 10⁻⁵ −1.21096 × 10⁻⁴ −3.31436 × 10⁻⁵ −2.71845 × 10⁻⁵ A₆−1.63342 × 10⁻⁷ −3.14892 × 10⁻⁸   2.15656 × 10⁻⁶ −1.24138 × 10⁻⁶−6.16672 × 10⁻⁶ A₈   0.000   7.47008 × 10⁻⁹ −1.23897 × 10⁻⁷ −6.21293 ×10⁻⁹   1.14404 × 10⁻⁷ A₁₀   2.47553 × 10⁻¹²   0.000   1.80977 × 10⁻⁹  5.65326 × 10⁻¹⁰ −6.55772 × 10⁻⁹

TABLE 1-2 12th surface 13th surface 14th surface 15th surface K −511.9970.910 −0.773  0.000 A₄ −1.35640 × 10⁻⁴ −1.71590 × 10⁻⁴ −1.36202 × 0.00010⁻³ A₆ −9.45635 × 10⁻⁶ −7.55572 × 10⁻⁶  7.62379 × 7.95903 × 10⁻⁵ 10⁻⁵A₈ −1.55393 × 10⁻⁷ −1.11729 × 10⁻⁸ 0.000 1.49209 × 10⁻⁷ A₁₀ 0.000−1.29134 × 10⁻⁹ 0.000 0.000

TABLE 2 Zoom Data (∞) WE ST TE f (mm) 7.32 12.40 20.95 F_(NO) 1.86 2.573.86 2ω(°) 66.55 39.00 23.69 d₃ 19.41 10.28 5.74 d₉ 2.74 5.59 14.38 d₁₃1.12 4.30 5.22 d₁₅ 2.42 1.20 0.54

EXAMPLE 2

r₁ = −20.816* d₁ = 0.90 n_(d1) = 1.43875 v_(d1) = 94.93 r₂ = 25.057* d₂= variable r₃ = 37.240* d₃ = 1.66 n_(d2) = 1.69350 v_(d2) = 53.20 r₄ =−20.795* d₄ = 0.85 r₅ = ∞ (S) d₅ = 0.00 r₆ = 6.489 d₆ = 2.89 n_(d3) =1.88300 v_(d3) = 40.76 r₇ = 18.770 d₇ = 0.55 n_(d4) = 1.83918 v_(d4) =23.85 r₈ = 4.726* d₈ = variable r₉ = −7.273 d₉ = 0.80 n_(d5) = 1.92286v_(d5) = 18.90 r₁₀ = −10.260 d₁₀ = 0.14 r₁₁ = 73.301* d₁₁ = 2.89 n_(d6)= 1.69350 v_(d6) = 53.20 r₁₂ = −8.705* d₁₂ = variable r₁₃ = 51.991* d₁₃= 1.00 n_(d7) = 1.69350 v_(d7) = 53.20 r₁₄ = 82.598* d₁₄ = variable r₁₅= ∞ d₁₅ = 0.74 n_(d8) = 1.54771 v_(d8) = 62.84 r₁₆ = ∞ d₁₆ = 0.50 r₁₇ =∞ d₁₇ = 0.50 n_(d9) = 1.51633 v_(d9) = 64.14 r₁₈ = ∞ d₁₈ = 0.55 r₁₉ = ∞(I)

TABLE 3-1 Aspherical coefficient 1st surface 2nd surface 3rd surface 4thsurface 8th surface K 1.180 −1.851 0.345 −19.177 0.046 A₄   1.40655 ×10⁻⁴   7.57636 × 10⁻⁵ −1.00415 × 10⁻⁴ −2.82138 × 10⁻⁴ −7.00739 × 10⁻⁵ A₆−1.80459 × 10⁻⁷   8.16426 × 10⁻⁷   9.13285 × 10⁻⁷   6.17656 × 10⁻⁶−7.43442 × 10⁻⁸ A₈ 0.000 −3.52579 × 10⁻⁹ −5.30604 × 10⁻⁸ −2.15982 × 10⁻⁷  3.15359 × 10⁻⁸ A₁₀ 0.000   0.000 −1.70089 × 10⁻⁹   1.04026 × 10⁻⁹  2.80403 × 10⁻⁸

TABLE 3-2 11th surface 12th surface 13th surface 14th surface K 9.9000.071 −3.830  0.000 A₄ −1.65424 × 10⁻⁴ 1.40802 × 10⁻⁴ −1.61854 × 0.00010⁻⁴ A₆ −2.62280 × 10⁻⁶ −1.28528 × 10⁻⁶ −4.23404 × 0.000 10⁻⁶ A₈ 0.0000.000 0.000 −1.27169 × 10⁻⁷ A₁₀ 0.000 0.000 0.000 0.000

TABLE 4 Zoom Data (∞) WE ST TE f (mm) 8.14 13.53 23.43 F_(NO) 1.85 2.443.48 2ω(°) 61.93 35.96 21.05 d₂ 21.66 11.45 4.17 d₈ 4.72 10.20 18.25 d₁₂0.90 1.21 2.48 d₁₄ 3.14 2.14 0.33

EXAMPLE 3

r₁ = −28.621* d₁ = 0.90 n_(d1) = 1.43875 v_(d1) = 94.93 r₂ = 13.270* d₂= variable r₃ = 18.910* d₃ = 1.83 n_(d2) = 1.76802 v_(d2) = 49.24 r₄ =−52.548* d₄ = 0.10 r₅ 7.084 d₅ = 2.89 n_(d3) = 1.88300 v_(d3) = 40.76 r₆= 27.980 d₆ = 0.55 n_(d4) = 1.83918 v_(d4) = 23.85 r₇ = 5.338* d₇ = 1.72r₈ = ∞ (S) d₈ = variable r₉ = −7.790 d₉ = 0.80 n_(d5) = 1.92286 v_(d5) =18.90 r₁₀ = −11.396 d₁₀ = 0.15 r₁₁ = 60.657* d₁₁ = 2.34 n_(d6) = 1.76802v_(d6) = 49.24 r₁₂ = −11.972* d₁₂ = variable r₁₃ = −26.874* d₁₃ = 1.00n_(d7) = 1.69350 v_(d7) = 53.20 r₁₄ = −17.612* d₁₄ = variable r₁₅ = ∞d₁₅ = 0.74 n_(d8) = 1.54771 v_(d8) = 62.84 r₁₆ = ∞ d₁₆ = 0.50 r₁₇ = ∞d₁₇ = 0.50 n_(d9) = 1.51633 v_(d9) = 64.14 r₁₈ = ∞ d₁₈ = 0.55 r₁₉ = ∞(I)

TABLE 5-1 Aspherical coefficient 1st surface 2nd surface 3rd surface 4thsurface 7th surface K −0.134 −1.454 −0.093 −18.402 0.004 A₄ 2.47196 ×10⁻⁷   1.35646 × 10⁻⁵   3.65504 × 10⁻⁵   3.23935 × 10⁻⁵ 1.46877 × 10⁻⁴A₆ 2.34297 × 10⁻⁷ −1.44746 × 10⁻⁷ −1.10311 × 10⁻⁷ −6.55955 × 10⁻⁷8.79444 × 10⁻⁶ A₈   0.000   6.88829 × 10⁻⁹ −4.25458 × 10⁻⁸ −3.93067 ×10⁻⁸ 1.86813 × 10⁻⁷ A₁₀   0.000   0.000   2.18338 × 10⁻¹⁰   4.20213 ×10⁻¹⁰ 8.06203 × 10⁻⁹

TABLE 5-2 11th surface 12th surface 13th surface 14th surface K −12.098−0.296 −5.302   0.000 A₄ −1.37660 × −5.40491 × 10⁻⁵ −3.55522 × 10⁻⁴0.000 10⁻⁴ A₆ 1.15212 × −2.16122 × 10⁻⁶   2.30162 × 10⁻⁵ 2.63358 × 10⁻⁶10⁻⁵ A₈ −2.15963 × −3.79109 × 10⁻⁸ 0.000 1.38995 × 10⁻⁷ 10⁻⁸ A₁₀   0.000 −2.42168 × 10⁻⁹ 0.000 0.000

TABLE 6 Zoom Data (∞) WE ST TE f (mm) 8.14 14.00 23.40 F_(NO) 1.86 2.313.68 2ω (°) 60.88 35.28 21.40 d₂ 20.49 6.87 5.23 d₈ 4.12 3.63 17.92 d₁₁1.11 7.40 5.08 d₁₄ 3.45 1.58 0.10

EXAMPLE 4

r₁ = −22.456* d₁ = 0.90 n_(d1) = 1.43875 v_(d1) = 94.93 r₂ = 14.994* d₂= variable r₃ = 13.771* d₃ = 2.19 n_(d2) = 1.76802 v_(d2) = 49.24 r₄ =−39.652* d₄ = 0.10 r₅ = 6.603* d₅ = 2.89 n_(d3) = 1.80610 v_(d3) = 40.92r₆ = 36.989 d₆ = 0.50 n_(d4) = 2.00069 v_(d4) = 25.46 r₇ = 4.970 d₇ =1.72 r₈ = ∞ (S) d₈ = variable r₉ = −8.900 d₉ = 0.80 n_(d5) = 1.92286v_(d5) = 18.90 r₁₀ = −16.301 d₁₀ = 0.18 r₁₁ = 45.839* d₁₁ = 2.55 n_(d6)= 1.80610 v_(d6) = 40.92 r₁₂ = −11.204* d₁₂ = variable r₁₃ = −11.989*d₁₃ = 1.00 n_(d7) = 1.52542 v_(d7) = 55.78 r₁₄ = −8.434* d₁₄ = variabler₁₅ = ∞ d₁₅ = 0.74 n_(d8) = 1.54771 v_(d8) = 62.84 r₁₆ = ∞ d₁₆ = 0.50r₁₇ = ∞ d₁₇ = 0.50 n_(d9) = 1.51633 v_(d9) = 64.14 r₁₈ = ∞ d₁₈ = 0.36r₁₉ = ∞ (I)

TABLE 7-1 Aspherical coefficient 1st surface 2nd surface 3rd surface 4thsurface 5th surface K −0.459 −1.934 −0.157 −17.823 0.201 A₄ 2.33118 ×10⁻⁵   3.16423 × 10⁻⁵   1.98169 × 10⁻⁵ −1.06473 × 10⁻⁵ −1.48728 × 10⁻⁴A₆ 2.15920 × 10⁻⁷ −2.27645 × 10⁻⁷ −2.11464 × 10⁻⁶ −3.59679 × 10⁻⁶−4.66395 × 10⁻⁶ A₈   0.000   1.23376 × 10⁻⁸ −7.88182 × 10⁻⁸   3.36460 ×10⁻⁸   1.36528 × 10⁻⁸ A₁₀ 5.54144 × 10⁻¹³   0.000   1.28470 × 10⁻⁹  1.43653 × 10⁻¹⁰ −1.08445 × 10⁻⁹

TABLE 7-2 11th surface 12th surface 13th surface 14th surface K −11.706−0.766 −3.556   0.000 A₄ −1.64483 × −6.30426 × 10⁻⁵ −1.01455 × 10⁻³0.000 10⁻⁴ A₆ −2.88572 × −6.34815 × 10⁻⁶   5.08647 × 10⁻⁵ 4.24264 × 10⁻⁶10⁻⁵ A₈ −2.78723 × −5.34397 × 10⁻⁸ 0.000 2.17708 × 10⁻⁷ 10⁻⁷ A₁₀   0.000−2.91352 × 10⁻⁹ 0.000 0.000

TABLE 8 Zoom Data (∞) WE ST TE f (mm) 8.14 13.86 23.36 F_(NO) 1.86 2.413.84 2ω (°) 60.97 35.69 21.53 d₂ 20.73 8.61 6.38 d₈ 3.43 4.36 17.08 d₁₂1.29 6.78 4.89 d₁₄ 3.26 1.29 0.09

EXAMPLE 5

r₁ = −22.732* d₁ = 0.90 n_(d1) = 1.43875 v_(d1) = 94.93 r₂ = 14.930* d₂= variable r₃ = 13.675* d₃ = 2.22 n_(d2) = 1.74320 v_(d2) = 49.34 r₄ =−35.635* d₄ = 0.10 r₅ 6.567* d₅ = 2.89 n_(d3) = 1.80610 v_(d3) = 40.92r₆ = 36.857 d₆ = 0.50 n_(d4) = 2.00069 v_(d4) = 25.46 r₇ = 4.934 d₇ =1.72 r₈ = ∞ (S) d₈ = variable r₉ = −8.940 d₉ = 0.80 n_(d5) = 1.92286v_(d5) = 18.90 r₁₀ = −16.369 d₁₀ = 0.18 r₁₁ = 45.839* d₁₁ = 2.55 n_(d6)= 1.80610 v_(d6) = 40.92 r₁₂ = −11.200* d₁₂ = variable r₁₃ = −10.490*d₁₃ = 1.00 n_(d7) = 1.52542 v_(d7) = 55.78 r₁₄ = −7.694* d₁₄ = variabler₁₅ = ∞ d₁₅ = 0.74 n_(d8) = 1.54771 v_(d8) = 62.84 r₁₆ = ∞ d₁₆ = 0.50r₁₇ = ∞ d₁₇ = 0.50 n_(d9) = 1.51633 v_(d9) = 64.14 r₁₈ = ∞ d₁₈ = 0.49r₁₉ = ∞ (I)

TABLE 9-1 Aspherical coefficient 1st surface 2nd surface 3rd surface 4thsurface 5th surface K −0.515 −2.154 −0.175 −17.795 0.190 A₄   3.92602 ×10⁻⁵   5.13992 × 10⁻⁵ −7.40812 × 10⁻⁶ −1.27019 × 10⁻⁵ −1.08305 × 10⁻⁴ A₆−1.48623 × 10⁻⁸ −9.41584 × 10⁻⁸ −3.56080 × 10⁻⁷ −4.94424 × 10⁻⁷ −2.85168× 10⁻⁶ A₈   0.000   5.04242 × 10⁻⁹ −2.19131 × 10⁻⁸ −7.21058 × 10⁻⁹−4.27801 × 10⁻⁸ A₁₀   1.85395 × 10⁻¹²   0.000 −7.65694 × 10⁻¹¹ −1.04401× 10⁻¹¹ −1.92590 × 10⁻⁹

TABLE 9-2 11th surface 12th surface 13th surface 14th surface K −11.837−0.838 −2.977   0.000 A₄ −1.75086 × 10⁻⁴ −6.93379 × 10⁻⁵ −1.09868 × 10⁻³0.000 A₆ −2.27012 × 10⁻⁶ −6.51775 × 10⁻⁶   5.00073 × 10⁻⁵ 4.46816 × 10⁻⁵A₈ −3.09026 × 10⁻⁷ −5.91578 × 10⁻⁸ 0.000 1.02875 × 10⁻⁷ A₁₀   0.000−3.02570 × 10⁻⁹ 0.000 0.000

TABLE 10 Zoom Data (∞) WE ST TE f (mm) 8.14 13.82 23.36 F_(NO) 1.86 2.423.85 2ω (°) 60.80 35.73 21.46 d₂ 20.73 8.82 6.35 d₈ 3.37 4.61 17.03 d₁₂1.25 6.45 4.81 d₁₄ 3.21 1.29 0.07

EXAMPLE 6

r₁ = −22.016* d₁ = 0.90 n_(d1) = 1.43875 v_(d1) = 94.93 r₂ = 15.461* d₂= variable r₃ = 14.701* d₃ = 2.06 n_(d2) = 1.74320 v_(d2) = 49.34 r₄ =−32.999* d₄ = 0.10 r₅ 6.405* d₅ = 2.89 n_(d3) = 1.80610 v_(d3) = 40.92r₆ = 33.244 d₆ = 0.50 n_(d4) = 2.00069 v_(d4) = 25.46 r₇ = 4.856 d₇ =1.72 r₈ = ∞ (S) d₈ = variable r₉ = −8.940 d₉ = 0.80 n_(d5) = 1.92286v_(d5) = 18.90 r₁₀ = −16.611 d₁₀ = 0.18 r₁₁ = 45.839* d₁₁ = 2.55n_(d6 = 1.80610) v_(d6) = 40.92 r₁₂ = −11.009* d₁₂ = variable r₁₃ =−10.879* d₁₃ = 1.00 n_(d7) = 1.52542 V_(d7) = 55.78 r₁₄ = −7.731* d₁₄ =variable r₁₅ = ∞ d₁₅ = 0.74 n_(d8) = 1.54771 v_(d8) = 62.84 r₁₆ = ∞ d₁₆= 0.50 r₁₇ = ∞ d₁₇ = 0.50 n_(d9) = 1.51633 v_(d9) = 64.14 r₁₈ = ∞ d₁₈ =0.53 r₁₉ = ∞ (I)

TABLE 11-2 Aspherical coefficient 1st surface 2nd surface 3rd surface4th surface 5th surface K −0.519 −2.161 −0.175 −17.775 0.037 A₄ 3.69695× 10⁻⁵   4.21993 × 10⁻⁵ −9.06679 × 10⁻⁶ −2.80828 × 10⁻⁵ −3.97693 × 10⁻⁵A₆ 5.65774 × 10⁻⁸ −1.75597 × 10⁻⁷ −3.53110 × 10⁻⁷ −1.49749 × 10⁻⁷−1.02246 × 10⁻⁶ A₈   0.000   8.97310 × 10⁻⁹ −2.44657 × 10⁻⁸ −1.08247 ×10⁻⁸ −1.04292 × 10⁻⁹ A₁₀ 3.73887 × 10⁻¹²   0.000   2.47234 × 10⁻¹⁰  1.49523 × 10⁻¹⁰ −2.35540 × 10⁻¹³

TABLE 11-2 11th surface 12th surface 13th surface 14th surface K −11.838−0.837 −2.908   0.000 A₄ −1.64575 × −6.41167 × 10⁻⁵ −1.08544 × 10⁻³0.000 10⁻⁴ A₆ −3.82233 × −6.74867 × 10⁻⁶ 4.99868 × 10⁻⁵ 4.25126 × 10⁻⁶10⁻⁵ A₈ −2.40636 × −4.23546 × 10⁻⁸ 0.000 1.52833 × 10⁻⁷ 10⁻⁷ A₁₀   0.000 −2.74519 × 10⁻⁹ 0.000 0.000

TABLE 12 Zoom Data (∞) WE ST TE f (mm) 8.14 13.81 23.37 F_(NO) 1.85 2.473.85 2ω (°) 60.83 35.75 21.47 d₂ 20.70 9.76 6.47 d₈ 3.54 6.20 17.38 d₁₂1.23 5.56 4.71 d₁₄ 3.18 1.24 0.03

EXAMPLE 7

r₁ = −22.274* d₁ = 0.90 n_(d1) = 1.43875 v_(d1) = 94.93 r₂ = 15.613* d₂= variable r₃ = 14.914* d₃ = 2.05 n_(d2) = 1.74320 v_(d2) = 49.34 r₄ =−36.211* d₄ = 0.10 r₅ 6.740* d₅ = 2.89 n_(d3) = 1.88300 V_(d3) = 40.76r₆ = 30.586 d₆ = 0.50 n_(d4) = 2.00069 v_(d4) = 25.46 r₇ = 4.878 d₇ =1.72 r₈ = ∞ (S) d₈ = variable r₉ = −8.330 d₉ = 0.80 n_(d5) = 1.94595v_(d5) = 17.98 r₁₀ = −14.723 d₁₀ = 0.18 r₁₁ = 60.339* d₁₁ = 2.55 n_(d6)= 1.88300 v_(d6) = 40.76 r₁₂ = −11.469* d₁₂ = variable r₁₃ = −11.106*d₁₃ = 1.00 n_(d7) = 1.52542 v_(d7) = 55.78 r₁₄ = −7.881* d₁₄ = variabler₁₅ = ∞ d₁₅ = 0.74 n_(d8) = 1.54771 v_(d8) = 62.84 r₁₆ = ∞ d₁₆ = 0.50r₁₇ = ∞ d₁₇ = 0.50 n_(d9) = 1.51633 v_(d9) = 64.14 r₁₈ = ∞ d₁₈ = 0.40r₁₉ = ∞ (I)

TABLE 13-1 Aspherical coefficient 1st surface 2nd surface 3rd surface4th surface 5th surface K −0.518 −2.161 −0.175 −17.775 0.036 A₄  4.88141 × 10⁻⁵   6.44536 × 10⁻⁵ −1.92171 × 10⁻⁵ −1.94577 × 10⁻⁵−2.54431 × 10⁻⁵ A₆ −3.21382 × 10⁻⁸ −2.46896 × 10⁻⁷ −3.89730 × 10⁻⁷−2.58431 × 10⁻⁷ −5.58730 × 10⁻⁷ A₈   0.000   7.75334 × 10⁻⁹ −1.82966 ×10⁻⁸ −1.15784 × 10⁻⁸ −5.36386 × 10⁻¹⁰ A₁₀   4.02767 × 10⁻¹²   0.000  1.26317 × 10⁻¹⁰   1.32488 × 10⁻¹⁰ −6.90965 × 10⁻¹²

TABLE 13-2 11th surface 12th surface 13th surface 14th surface K −11.838−0.837 −2.908   0.000 A₄ −1.37364 × −5.64622 × 10⁻⁵ −9.86766 × 10⁻⁴0.000 10⁻⁴ A₆ −4.56316 × −6.19494 × 10⁻⁵   3.81895 × 10⁻⁵ 3.39609 × 10⁻⁶10⁻⁵ A₈ −3.54608 ×   3.58402 × 10⁻⁸ 0.000 5.27968 × 10⁻⁸ 10⁻⁸ A₁₀  0.000 −1.10103 × 10⁻⁹ 0.000 0.000

TABLE 14 Zoom Data (∞) WE ST TE f (mm) 8.10 13.65 23.32 F_(NO) 1.86 2.463.86 2ω (°) 61.72 36.45 21.68 d₂ 20.69 9.75 6.43 d₈ 3.59 6.22 17.41 d₁₂1.26 5.55 4.68 d₁₄ 3.39 1.39 0.04

Aberration diagrams of Examples 1 to 7 when focused on the infiniteobject as described above are shown in FIGS. 8A to 14C. Among theseaberration diagrams, FIGS. 8A, 9A, . . . show a spherical aberration(SA), an astigmatism (FC), a distortion (DT) and a chromatic aberrationof magnification (CC) in a wide-angle end, FIGS. 8B, 9B, . . . show theaberrations in an intermediate state and FIGS. 8C, 9C, . . . show theaberrations in a telephoto end. In the drawings, “FIY” is a maximumimage height.

Next, values of the conditions (1) to (16) in the above examples will bedescribed.

TABLE 15 Conditions Example 1 Example 2 Example 3 Example 4 Example 5Example 6 Example 7 (1) −2.565 −2.728 −2.261 −1.966 −1.976 −1.965 −1.946(2) −5.702 −5.869 −5.321 −3.405 −3.407 −3.331 −3.606 (3) 1.923 1.9231.923 1.923 1.923 1.923 1.946 (4) 18.900 18.900 18.900 18.900 18.90018.900 17.984 (5) 0.610 0.579 0.718 0.633 0.626 0.646 0.656 (6) — 18.90018.900 18.900 18.900 18.900 94.930 (7) 0.155 −0.092 0.366 0.199 0.2070.175 0.176 (8) 0.594 0.581 0.656 0.611 0.606 0.597 0.602 (9) 2.0011.839 1.839 2.001 2.001 2.001 2.001 (10)  25.458 23.855 23.855 25.45825.458 25.458 25.458 (11)  −2.533 −3.164 −2.522 −2.500 −2.505 −2.525−2.564 (12)  1.707 1.774 1.693 1.667 1.668 1.682 1.696 (13)  2.770 1.8882.497 2.358 2.349 2.322 2.305 (14)  5.815 5.451 5.371 5.358 5.358 5.3545.397 (15)  2.028 1.666 1.827 1.846 1.845 1.852 1.849 (16)  10.81610.072 9.983 9.965 9.959 9.924 10.025

These examples are directed to a compact zoom lens system having a zoomratio which is as large as about threefold; an angle of field which isas large as about 60° in the wide-angle end; a full aperture F-valuewhich is as bright as about 1.8 in the wide-angle end; and asatisfactory optical performance in the whole magnification changeregion and the whole photographing distance.

The above zoom lens systems can be combined with an image sensor toconstitute an electronic image pickup unit. In this case, the imagesensor is disposed at a position where an object image formed by thezoom lens system is received.

Moreover, the above zoom lens system can be used in a photographingapparatus in which the object image is formed by the zoom lens systemand received by the image sensor to photograph the object. Specificexamples of the photographing apparatus include an electronic camerasuch as a digital camera; and information processing units such as apersonal computer in which a camera is incorporated and portableterminal devices, for example, a cellular phone and a personal digitalassistant (PDA) in which a camera is incorporated.

FIGS. 15 to 17 are conceptual diagrams showing a constitution of adigital camera in which the zoom lens system according to the presentinvention is incorporated as a photographing optical system. FIG. 15 isa front perspective view showing an appearance of a digital camera; FIG.16 is a rear view of the camera; and FIG. 17 is a schematic sectionalview showing a constitution of the digital camera. In addition, in FIGS.15 and 17, a non-collapsible state of the photographing optical system41 is shown. In this example, the digital camera 40 includes aphotographing optical system 41 positioned along a photographing opticalpath 42; a finder optical system 43 positioned along an optical path 44for a finder; a shutter button 45; a flash lamp 46; a liquid crystaldisplay monitor 47; a focal length change button 61; a setting changeswitch 62 and the like. In a case where the photographing optical system41 is collapsed, when a cover 60 is slid, the photographing opticalsystem 41, the finder optical system 43 and the flash lamp 46 arecovered with the cover 60. Moreover, when the cover 60 is opened tobring the camera 40 into a photographing state, the photographingoptical system 41 is brought into the non-collapsed state shown in FIG.17. When the shutter button 45 disposed at an upper portion of thecamera 40 is pressed, the photographing is performed through thephotographing optical system 41, for example, the zoom lens system ofExample 1, in response to the pressed button. An object image is formedby the photographing optical system 41 on an image pickup surface (aphotoelectric conversion surface) of a CCD image sensor 49 via a lowpass filter F and a cover glass C provided with a wavelength bandrestrictive coating. This object image received by this CCD image sensor49 is displayed as an electronic image in the liquid crystal displaymonitor 47 disposed in a rear surface of the camera via a processingsection 51. This processing section 51 is connected to a recordingsection 52, and the photographed electronic image can be recorded. It isto be noted that this recording section 52 may be integrated with theprocessing section 51, or the sections may separately be arranged. As amedium in which the electronic image is recorded, a hard disk drive(HDD), a memory card, an optical disk such as a DVD±RW or the like isusable. A film camera may be constituted in which a silver halide filmis disposed Instead of the CCD image sensor 49.

Furthermore, an objective optical system 53 for the finder is disposedalong the optical path 44 for the finder. The objective optical system53 for the finder is constituted of a zoom optical system including aplurality of lens units (three lens units in the drawing) and an imageerecting prism system 55 constituted of image erecting prisms 55 a, 55 band 55 c. In the system, a focal length changes in conjunction with thezoom lens system of the photographing optical system 41. The objectimage is formed by the objective optical system 53 for the finder on aview field frame 57 of the image erecting prism system 55. Behind theimage erecting prism system 55, an eyepiece optical system 59 isdisposed which guides an erected image into an observer's eyeball E. Itis to be noted that a cover member 50 is disposed on an emission side ofthe eyepiece optical system 59.

FIG. 18 shows a schematic block diagram of a main part of a controlsystem of the digital camera 40. It is to be noted that an input sectiontypified by the shutter button 45 is denoted with reference numeral 500.A CPU 51 corresponds to the processing section of FIG. 17. A recordingsection includes a memory card 521 and an external storage device (anoptical disk, an HDD or the like) 522. A display processing section 80is omitted from FIG. 17. The section performs display processing todisplay an image or information in the display section 47 by use of anoutput from the CPU 51. In a case where the CPU 51 judges that theshutter button 45 of the input section 500 is pressed, appropriatecontrol values such as a shutter speed and a aperture diameter arecalculated using information obtained from a photometry system (notshown). After the calculation, a shutter and an aperture stop arecontrolled based on the control values.

The digital camera is an example of an electronic camera including thezoom lens system according to the present invention; an image sensordisposed at a position where an object image formed by the zoom lenssystem is received; a CPU which processes an electric signalphotoelectrically converted by the image sensor; a display element whichdisplays the object image received by the image sensor so as to observethe image; a recording processing section which records the object imagereceived by the image sensor in a recording medium; and the recordingmedium incorporated in the electronic camera and/or constituted so as tobe detachably attached to the electronic camera in order to record imageinformation of the object image received by the image sensor. The CPUperforms control so as to displays the object image received by theimage sensor in the display element, and also performs control so as torecord the object image received by the image sensor in the recordingmedium.

Next, a cellular phone provided with a camera using the zoom lens systemaccording to the present invention will be described with reference toFIGS. 19 to 21. FIG. 19 is a front view of the cellular phone; FIG. 20is a sectional view of a photographing optical system incorporated inthe cellular phone; FIG. 21 is a side view of the cellular phone; andFIG. 22 is a schematic block diagram showing a main part of a controlsystem related to photographing, image recording and image display ofthe cellular phone.

As shown in FIGS. 19 to 21, a cellular phone 400 has a microphone 401which inputs operator's voice as information; a speaker 402 whichoutputs partner's voice; input keys 403 via which an operator inputsinformation; a monitor 404 which displays an image obtained byphotographing the operator, the surrounding scenery or the like, orinformation such as telephone numbers; a photographing optical system405; an antenna 406 which transmits and receives a communication radiowave; a processing section which processes image information,communication information, an input signal and the like; and a recordingsection which records the image. Here, the monitor 404 is a liquidcrystal displayed element. Here, the monitor 404 may be a transmissiontype liquid crystal display element which is illuminated from the rearby a backlight (not shown), a reflective type liquid crystal displayelement which reflects light entering the element from a front surfaceto display the information or the like.

The photographing optical system 405 has a photographing lens system 410including the zoom lens system according to the present inventiondisposed along a photographing optical path 407; and an image sensorchip 411 which receives an object image formed by the photographing lenssystem 410. A cover glass C is attached on the image sensor chip 411.These components are incorporated in the cellular phone 400.

Here, the image sensor chip 411 is fitted into a rear end of a lensbarrel 412 of the photographing lens system 410 through a on-touchoperation and constitutes an electronic image pickup unit 450 with thelens barrel and the photographing lens system. Therefore, centering ofthe photographing lens system 410 and the image sensor chip 411 need notbe adjusted, an interval between the image sensor chip 411 and thephotographing lens system need not be adjusted, and assembling isfacilitated. A cover glass 413 for protecting the photographing lenssystem 410 is disposed on a tip end of the lens barrel 412. It is to benoted that a driving mechanism of the zoom lens system in the lensbarrel 412 is omitted from the drawing.

The object image received by the image sensor chip 411 is input into theprocessing section via a terminal (not shown), and displayed as anelectronic image in the monitor 404 and/or a partner's monitor. In acase where the image is transmitted to the partner, a signal processingfunction of converting information of the object image received by theimage sensor chip 411 into a transmittable signal is included in theprocessing section.

FIG. 22 shows a schematic block diagram of the main part of the controlsystem related to the photographing, image recording and image displayof the cellular phone 400. It is to be noted that an input section suchas the input keys 403 is denoted with reference numeral 500. A CPU 415corresponds to the above processing section, and a memory card 521 andan external storage device (the HDD or the like) 522 correspond to therecording section. A display processing section 480 performs displayprocessing to display an image or information in a display section 404by use of an output from the CPU 415. In a case where the CPU 415 judgesthat information corresponding to a photographing instruction is inputfrom the input section 500, appropriate control values such as a shutterspeed and an aperture diameter are calculated using information obtainedfrom a photometry system (not shown). After the calculation, a shutterand an aperture stop are controlled based on the control values. It isto be noted that to simplify the constitution, one or both of theshutter speed control and the aperture value control can be omitted.

This cellular phone provided with the camera is an example of aninformation processing device including the zoom lens system accordingto the present invention; an image sensor disposed at a position wherean object image formed by the zoom lens system is received; a CPU whichprocesses an electric signal photoelectrically converted by the imagesensor; an input section which inputs an information signal to be inputinto the CPU by an operator; a display processing section which displaysan output from the CPU in a display unit (e.g., an LCD); and a recordingmedium which records the output from the CPU. The CPU is configured toperform control so as to display the object image received by the imagesensor in the display unit.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention. Rather, the scopeof the invention shall be defined as set forth in the following claimsand their legal equivalents. All such modifications as would be obviousto one skilled in the art are intended to be included within the scopeof the following claims.

1. A zoom lens system comprising, in order from an object side: a firstlens unit having a negative refractive power; a second lens unit havinga positive refractive power; and a third lens unit having a positiverefractive power, wherein a space between the lens units is changed toperform magnification change; a lens of the second lens unit closest toan image side has a concave surface which faces the image side; a lensof the third lens unit closest to the object side is a negative lenswhose concave surface faces the object side; and during themagnification change, the space between the second lens unit and thethird lens unit is larger in a telephoto end than in a wide-angle end.2. The zoom lens system according to claim 1, wherein the third lensunit is moved to perform focusing on an object at a short distance. 3.The zoom lens system according to claim 1, wherein the third lens unitincludes a negative lens and a positive lens in order from the objectside.
 4. The zoom lens system according to claim 3, wherein the negativelens and the positive lens of the third lens unit satisfy the followingcondition:−4.2<f _(3n) /f _(3p)<−1.1  (1), in which f_(3n) is a focal length ofthe negative lens of the third lens unit, and f_(3p) is a focal lengthof the positive lens of the third lens unit.
 5. The zoom lens systemaccording to claim 1, wherein the negative lens of the third lens unitclosest to the object side satisfies the following condition:−7.90<SF _(3n)<−1.20  (2), in which SF_(3n) is defined bySF_(3n)=(R_(31f)+R_(31r))/(R_(31f)−R_(31r)) and in which R_(31f),R_(31r) are paraxial radii of curvatures of an object-side surface andan image-side surface of the negative lens of the third lens unit,respectively.
 6. The zoom lens system according to claim 1, wherein thenegative lens of the third lens unit closest to the object sidesatisfies the following conditions:1.75<n_(d3n)<2.20  (3); and13.0<v_(d3n)<33.0  (4), in which n_(d3n) and v_(d3n) are a refractiveindex and the Abbe number of the negative lens of the third lens unitclosest to the object side for the d-line, respectively.
 7. The zoomlens system according to claim 1, wherein the following condition issatisfied:0.35<d ₂₃ /f _(w)<1.25  (5), in which d₂₃ is an axial space between thesecond lens unit and the third lens unit in the wide-angle end, andf_(w) is a focal length of the zoom lens system in the wide-angle end.8. The zoom lens system according to claim 1, wherein the first lensunit includes two lenses or less.
 9. The zoom lens system according toclaim 8, wherein the first lens unit includes one negative lens.
 10. Thezoom lens system according to claim 9, wherein the negative lens of thefirst lens unit satisfies the following condition:75.0<v_(d1n)<105.0  (6), in which V_(d1n) is the Abbe number of thenegative lens of the first lens unit.
 11. The zoom lens system accordingto claim 10, wherein the negative lens of the first lens unit satisfiesthe following condition:0.01<SF_(1n)<1.00  (7), in which SF_(1n) is defined bySF_(1n)=(R_(11f)+R_(11r))/(R_(11f)−R_(11r)) and in which R_(11f),R_(11r) are paraxial radii of curvatures of an object-side surface andan image-side surface of the negative lens of the first lens unit,respectively.
 12. The zoom lens system according to claim 8, wherein thefirst lens unit includes a cemented lens of a negative lens and apositive lens.
 13. The zoom lens system according to claim 1, wherein anaperture stop is disposed between the second lens unit and the thirdlens unit.
 14. The zoom lens system according to claim 1, wherein thefollowing condition is satisfied:5.0<Fno _(w) ×L _(w) /f _(w)<17.0  (16), in which Fno_(w) is a fullaperture F-value in the wide-angle end, L_(w) is the total length of thezoom lens system in the wide-angle end, and f_(w) is a focal length ofthe zoom lens system in the wide-angle end.
 15. An electronic imagepickup unit comprising: the zoom lens system according to claim 1; andan image sensor disposed at a position where an object image formed bythe zoom lens system is received.
 16. An information processing devicecomprising: the zoom lens system according to claim 1; an image sensordisposed at a position where an object image formed by the zoom lenssystem is received; a CPU which processes an electric signalphotoelectrically converted by the image sensor; an input section whichinputs an information signal to be input into the CPU by an operator;display processing section for displaying an output from the CPU in adisplay unit; and a recording medium which records the output from theCPU, wherein the CPU is configured to perform control so as to displaythe object image received by the image sensor in the display unit. 17.The information processing device according to claim 16, which is aportable terminal device.
 18. An electronic camera device comprising:the zoom lens system according to claim 1; an image sensor disposed at aposition where an object image formed by the zoom lens system isreceived; a CPU which processes an electric signal photoelectricallyconverted by the image sensor; a display element which displays theobject image received by the image sensor so as to observe the image;and a recording processing section which records the object imagereceived by the image sensor in a recording medium; and the recordingmedium incorporated in the electronic camera device and/or constitutedso as to be detachably attached to the electronic camera device in orderto record image information of the object image received by the imagesensor, wherein the CPU is configured to perform control so as todisplay the object image received by the image sensor in the displayelement and to record the object image received by the image sensor inthe recording medium.